Pong/Assets/Scripts/Game/Wormhole.cs

using System.Collections;
using System.Linq;
using Unity.Netcode;
using UnityEngine;

namespace Game {
	public class Wormhole : NetworkBehaviour {

		public float duration = 10;

		private const float MaxSize = 10;

		private float size;
		public float Size {
			get => size;
			set {
				size = value;
				transform.localScale = new Vector3(size, size, 1);
			}
		}

		private float Radius => Size / 2;
		
		private static float CubicEaseInOut(float t, float b, float c, float d) {
			if ((t /= d / 2) < 1) return c / 2 * t * t * t + b;
			return c / 2 * ((t -= 2) * t * t + 2) + b;
		}
		
		private static float CircleEaseInOut(float t, float b, float c, float d) {
			if ((t /= d / 2) < 1) return -c / 2 * (Mathf.Sqrt(1 - t * t) - 1) + b;
			return c / 2 * (Mathf.Sqrt(1 - (t -= 2) * t) + 1) + b;
		}

		private IEnumerator Grow(float growTime) {
			float currentTime = 0;
			while (currentTime <= growTime) {
				Size = CircleEaseInOut(currentTime, 0, MaxSize, growTime);
				yield return new WaitForFixedUpdate();
				currentTime += Time.fixedDeltaTime;
			}
		}

		private IEnumerator Shrink(float shrinkTime) {
			float currentTime = 0;
			while (currentTime <= shrinkTime) {
				Size = CubicEaseInOut(currentTime, MaxSize, -MaxSize, shrinkTime);
				yield return new WaitForFixedUpdate();
				currentTime += Time.fixedDeltaTime;
			}
		}

		private IEnumerator Start() {
			Size = 0;
			yield return Grow(duration * 0.2f);
			yield return new WaitForSeconds(duration * 0.7f);
			yield return Shrink(duration * 0.1f);
		}

		private void FixedUpdate() {
			Vector2 thisPos = new Vector2(transform.position.x, transform.position.y);
			foreach (var ball in GameManager.Singleton.Balls) {
				Vector2 diff = thisPos - ball.Rb.position;
				if (diff.sqrMagnitude > Radius * Radius)
					continue;
				float dist = diff.magnitude;
				Vector2 force = diff.normalized / dist * (Size * 5);
				force = Vector2.ClampMagnitude(force, 15);
				ball.Rb.AddForce(force);
			}
		}
	}
}